Prawn: How to make “Leader dots” for Table of content?

Question

I'm using Prawn gem to generate PDF documents within my Rails Application. I've successfully created the PDFs But I have a table of contents and I wonder is it possible Or Is there is a way to create the leader dots effect in Prawn ?

Answer 1

Yes, there is a way to create the leader dots effect in Praw.

If you have:

1. the total available width
2. width of the table of content entry
3. width of the page number
4. width of a single leader dot

space_for_dots = 1. - 2. - 3.

dots = (space_for_dots / 4) * '.'

toc_entry = entry_string + dots + entry_page_number

---

To calculate the width of a string in prawn, you can use compute_width_of, which is part of the font classes.

An example for the picture you added could look like this:

def build_toc_entry(left_text, right_text, available_width, text_size)
  left_text_width = font(YOUR_FONT).compute_width_of(left_text, size: text_size)
  right_text_width = font(YOUR_FONT).compute_width_of(right_text, size: text_size)
  dot_width = font(YOUR_FONT).compute_width_of('.', size: text_size)
  space_width = font(YOUR_FONT).compute_width_of(' ', size: text_size)

  space_for_dots = available_width - left_text_width - right_text_width - space_width * 2
  dots = '.' * (space_for_dots / dot_width)

  "#{left_text} #{dots} #{right_text}" # return the finished toc entry
end

text 'Locate the information on the page indicated.'
text build_toc_entry('Leader Dots', '3', 350, 8)
text build_toc_entry('Dingbats', '5', 350, 8)
text build_toc_entry('Bullets', '8', 350, 8)

Answer 2

This is a little late but here is what I did to get the dots to align properly with only left side text. But I think it would be reasonably easy to modify for left and right text:

def build_dots(text, available_width, text_size)
        dots_hash = {}
        current_font = font.inspect.split('<')[1].split(':')[0].strip
      text_width = font(current_font).compute_width_of(text, size: text_size)
      dot_width = font(current_font).compute_width_of('.', size: text_size)
      space_width = font(current_font).compute_width_of(' ', size: text_size)

      space_for_dots = available_width - text_width - space_width * 2
      dots = '.' * (space_for_dots / dot_width)
      dots_width = font(current_font).compute_width_of(dots, size: text_size)
      dots_start = available_width - dots_width - (space_width * 2)
      dots_hash[:dots] = dots
      dots_hash[:position] = dots_start

      return dots_hash
end

    dot_values = build_dots(officer.title,150,text_size)
    p = 0
    float {
        text "#{officer.title}", size: text_size
    }

    indent(dot_values[:position]) do
        float {
            text dot_values[:dots], size: text_size
        }
    end

    p += 150
    indent(p,0) do
        text "#{officer.name}", size: text_size
    end